The present invention relates to a spectacle lens with a carrier rim region as well as a method for producing a spectacle lens with a carrier rim region.
The use of spectacle lenses with a carrier rim, to reduce the weight, especially of spectacle lenses for correcting extremely defective vision, like extreme myopia, or for patients having undergone gray cataract surgery without an implanted lens, has been proposed in the past.
DE 30 16 936 A1 describes spectacle lenses with atoric surfaces that are characterized by very good image-forming properties for a specific (central) area. WO 97/15857 describes double aspheric spectacle lenses. They are characterized in that the image-forming properties are very good in the central area, that at least indirect, orienting vision is just barely possible in the peripheral area, and the critical thickness is, nevertheless, reduced. DE 33 43 891 A describes a spectacle lens with a carrier rim. Carrier rim lenses (also called lenticular lenses) are spectacle lenses, in which only the central portion of the spectacle lens delivers the corresponding optical effect, whereby the outer area surrounding the central portion is used merely for fastening in the spectacle frame. Owing to the carrier rim, the center thickness is reduced in the spectacle lens, according to DE 33 43 891 A1, at the expense of the image-forming quality.
An object of the present invention is to provide a spectacle lens as well as a method for calculating a spectacle lens in which, due to a carrier rim, the cosmetic properties, especially the edge thickness, its variation and/or the center thickness, are significantly improved without significantly influencing or having a negative impact on the image-forming properties.
This object has been achieved by way of a spectacle lens, and method for producing that lens having an object-sided front face and an eye-sided rear face, wherein at least the rear face has a viewing region that contributes to the optical effect of the spectacle lens, and a carrier rim region that at least partially surrounds the viewing region and which does not significantly contribute to the optical effect of the spectacle lens, and the rear face of the spectacle lens in the carrier rim region is designed substantially from a cosmetic viewpoint without consideration of the optical image-forming properties.
The present invention is based on the understanding that the peripheral area of the rear face (i.e., the eye-sided face of the spectacle lens), especially in spectacle lenses with negative effect, has an area that is not used significantly for seeing. Therefore, the rear face of the spectacle lens in this area may be especially designed so that the cosmetic properties of the spectacle lens are improved without significantly influencing its optical properties or rather its image-forming quality. This area constitutes the spectacle lens' carrier rim region that, together with the front face, forms a carrier rim. Cosmetic properties are defined in particular as the edge thickness, its variation, the center thickness, the weight and the volume of the spectacle lens.
The viewing region is preferably separated from the carrier rim region on the rear face of the spectacle lens by a dividing curve that connects the penetrating points of the main rays to the rear face. These main rays (hereinafter referred to as the outermost peripheral rays) just barely pass, under direct vision, through the point of rotation Z′ of the eye when the spectacle lens is in use position in front of an eye of a spectacle wearer; or in an especially preferred case these outermost peripheral rays just barely pass, under indirect vision, through the center of the entrance pupil of the eye. Then the carrier rim region extends from the dividing curve radially to the outside as far as the rim of the spectacle lens or preferably as far as a curve (peripheral curve) that matches the rim of the spectacle lens in the encased state. The dividing curve is an imaginary curve on the rear face.
Under indirect vision and on viewing through the accommodating point, the entrance pupil of the eye constitutes the aperture stop of the system, comprising the spectacle lens and the eye, and, thus, defines the course of the main rays. Under indirect vision the filed of vision is defined by those main rays that just barely penetrate both the front and the rear face of the spectacle lens and pass through the center of the entrance pupil of an eye when the spectacle lens is in use position. These (critical) main rays are called the outermost peripheral rays within the meaning of this invention. Since in this case the object-sided, outer axial object points (also called field points) do not pass through the center of the entrance pupil, in particular, the design of the rear face does not have any significant influence on the optical properties of the spectacle lens in an area that extends from the penetrating points of the outermost peripheral ray through the rear face radially to the rim of the spectacle lens. Therefore, under indirect vision this area forms preferably the carrier rim region.
Because it is more likely that indirect vision will be necessary on the periphery, the outermost peripheral rays are applied, under indirect vision, as the outermost peripheral rays when the spectacle lens is in use position. The result is a relatively large area (i.e., a relatively large carrier rim region) that may be used for improving the cosmetic properties.
Under indirect vision (i.e., especially when the eye is looking in the zero viewing direction), the small field of the perceivable region of interest is controlled by the head movements. However, under direct vision with the spectacle lens in use position it is not the head, but rather the eye, that performs the viewing movements in order to image, if possible, the objects of interest on the central area of the fovea. Under direct vision the eye rotates approximately about the optical point of rotation Z′ of the eye. As the apparent aperture stop, said point of rotation also brings about the position of the exit pupil of the system, comprising spectacle lens and eye, and in this way defines the course of the main rays and, therefore, also the course of the outermost peripheral rays. After the refraction through the spectacle lens, the outermost peripheral rays pass through the point of rotation Z′ of the eye. The penetrating points of the outermost peripheral rays through the rear face are spaced somewhat apart from the rim of the spectacle lens, so that the rear face has an area that extends from the penetrating points of the outermost peripheral rays through the rear face as far as the rim of the spectacle lens and that does not add, under direct vision, to the optical effect. In the case of direct vision this area constitutes the carrier rim region.
The calculation of the position of the dividing curve may be carried out on the basis of an average or conventional eye or according to the individual parameters of the eye of the respective spectacle wearer. For example, the so-called Gullstrand model eye may be used. The distance between the spectacle vertex and the entrance pupil of the model eye is then approximately HSA+3.05 mm, where HSA stands for the cornea-vertex-distance. The point of rotation of this average eye is approximately 13.5 mm behind the cornea, or at a standard HSA of 15 mm it is spaced 28.5 mm apart from the spectacle vertex. Since the entrance pupil is closer to the eye than the point of rotation of the eye, the optically non-useable area that constitutes the carrier rim region will be somewhat larger under indirect vision than under direct vision. The fovea exhibits usually an angular recess of 5 degrees. The course and the calculation of the outermost peripheral rays upon direct and indirect vision as well as the resulting dividing curve shall be explained in detail below.
Reference is made to Optik und Technik der Brille [Optics and the Technology of Spectacles] by Heinz Diepes and Ralf Blendowske, Optische Fachveröffentlichung GmbH, Heidelberg, 2002, especially with respect to the technical terms that are used and the model eye. In this respect, moreover, the information in this book represents an integral part of the disclosure of the present application.
Moreover, the spectacle lens exhibits a positive, negative, progressive, astigmatic and/or prismatic optical power.
The carrier rim region is designed preferably such that the shape and/or the design of the frame is taken into consideration. The shape of the frame, which is often referred to as the so-called discoid shape, is defined as a mathematically clear parameterization of the shape of the rim of the spectacle lens. The shape of the frame indicates how the round-shaped lens has to be machined on the rim so that the lens will fit into the spectacle frame. There exist, for example, round, oval or tear-shaped frames. The description of the shape of the frame will indicate whether it is, for example, a rimless frame or a very thick plastic frame. The edge thickness of the spectacle lens may be chosen to match the frame.
Therefore, it is especially advantageous to know the shape of the frame. Then the rear face in the carrier rim region may be produced so that the edge thickness of the spectacle lens or rather its variation in the encased state or rather along a curve that matches the rim of the spectacle lens in the encased case (hereinafter also referred to as the peripheral curve) is optimally contoured. However, the rear face in the carrier rim region may also be designed such that the edge thickness, its variation, etc., exhibit the predetermined optimal values for round-shaped spectacle lenses.
Furthermore, the rear face in the carrier rim region is designed preferably so that the individual parameters of the spectacle wearer may be considered. Individual parameters of the spectacle wearer are, for example, the distance between the cornea and the vertex, front inclination, pupil distance, lateral inclination, angle of the frame disc, distance of the point of rotation of the eye, length of the eye construction, distance of the object, etc. With these parameters, the exact course of the outermost peripheral rays in use position can be calculated or rather their penetrating points through the rear face and also the area may be used for improving the cosmetic properties. This enables an optimal design of the rear face in the carrier rim region and thus improved cosmetic properties of the spectacle lens. The calculation may, however, also be made with the aid of the standard values.
According to another preferred embodiment, the rear face of the spectacle lens is designed so that the rear face in the carrier rim region is joined at in a least once, preferably in a twice continuously differentiable manner to the rear face in the viewing region.
The rear face is designed preferably in such a manner that an edge thickness, edge thickness variation and/or center thickness of the spectacle lens may be reduced. Furthermore, the rear face in the carrier rim region may be designed preferably such that the volume and the mass of the spectacle lens may be reduced.
High demands with respect to not only the optical properties but also the cosmetic properties and the weight are placed on modern spectacle lenses. For aesthetic and tolerability reasons, the spectacle lenses ought to be as thin and light-weight as possible, while at the same time in particular the edge thickness ought to be minimized. Furthermore, the edge thickness ought to be designed uniformly with minimal variations.
Excessive center thickness and, based on the shape of the frame, non-uniform edge thickness, especially in spectacle lenses for hyperopia (i.e., spectacle lenses with positive optical effect), however, make the spectacle lenses look unappealing from a cosmetic viewpoint. In spectacle lenses for myopia (i.e., spectacle lenses with negative effect) the edge thickness and the non-uniform variation in the edge thickness, based on the shape of the frame, are the critical parameters. In both cases, the volume and, thus, also the weight of the spectacle lens increases, especially as the optical effects increase, a feature that may result in intolerability and rejection of the spectacle lens.
In spectacle lenses for spectacle wearers with defective vision due to astigmatism, the non-uniform variation of the edge thickness is the critical parameter. In spectacle lenses for heterophoria (i.e., spectacle lenses with prismatic effect) predominantly the non-uniform edge thickness but also the center thickness are the critical parameters. In spectacle lenses for presbyopia (i.e., spectacle lenses with progressive effect) predominantly the non-uniform variation of the edge thickness is the critical variable. Of course, in spectacle lenses with combined effects combinations of the listed requirements may also occur.
The rear face in the carrier rim region is designed, according to the present invention, so that the critical parameters for the indicated types of spectacle lenses fall within the predetermined intervals and/or may be met as much as possible.
The rear face in the carrier rim region is designed preferably such that the maximum edge thickness of the spectacle lens may be reduced by preferably at least 5%, especially 10%; and/or the variation in the edge thickness of the spectacle lens may be reduced by preferably at least 10%, especially 20%. The maximum center thickness of the spectacle lens may be reduced preferably by at least 3%, especially 5%. The specified reduction relates to a spectacle lens without a carrier rim as the initial variable.
Furthermore, the invention provides a method for producing a spectacle lens with an object-sided front face and an eye-sided rear face, wherein at least the rear face comprises                a viewing region, which contributes to the optical effect of the spectacle lens, and        a carrier rim region, which surrounds at least partially the viewing region and which does not significantly contribute to the optical effect of the spectacle lens.A calculation and/or optimization step of the rear face of the spectacle lens in the carrier rim region is/are carried out essentially from cosmetic viewpoints without considering the optical image-forming properties of the carrier rim region.        
Preferably the calculation and/or optimization step comprise or comprises the calculation of a dividing curve on the rear face of the spectacle lens between the viewing region and the carrier rim region in the shape of a curve that connects the penetrating points of the outermost peripheral rays to the rear face. The outermost peripheral rays just barely pass, under direct vision, through the point of rotation Z′ of the eye when the spectacle lens is in use position in front of an eye of a spectacle wearer; or in an especially preferred case, the outermost peripheral rays just barely pass, under indirect vision, through the center of the entrance pupil of the eye.
Furthermore, the calculation and/or optimization step preferably take or takes place in so that the shape and/or the design of the frame is/are taken into consideration. Then in particular, an optimal contour of the edge thickness of the spectacle lens or rather its variation in the encased state may be guaranteed.
The calculation and/or optimization step take(s) place in particular preferably in such a manner that the individual parameters of the spectacle wearer are considered. As a result, the outermost peripheral rays in use position can be calculated with high precision and, thus, the carrier rim region can be optimally designed.
The calculation and/or optimization step take or takes place most preferably so that the rear face in the carrier rim region is joined in a at least once, preferably in a twice continuously differentiable manner to the viewing region.
The calculation and/or optimization step may take place in such a manner that the parameters that are to be optimized according to cosmetic criteria are specified immediately during the optimization of the rear face. In this case, one assumes a surface extension for the rear face that must be flexible enough to enable the rear face in the carrier rim region to be suitably optimized in accordance with the predetermined parameters. Therefore, at least powers of the fourth order are needed especially in rotationally symmetrical aspheres. This procedure may be more advantageous especially with spectacle lenses with positive refractive power, because the optical effect of the spectacle lens changes as the critical parameters of the center thickness to be optimized according to cosmetic criteria changes.
The rear face in the carrier rim region can advantageously be optimized independently of the rear face in the viewing region. In other words, the calculation and/or optimization step of the rear face in the carrier rim region do or does not take place until after the calculation and/or the optimization of the rear face in the viewing region. Therefore, the carrier rim region, which is optimally shaped according to cosmetic criteria, can be adjoined to any specified rear face, and in particular independently of the shape of the rear face in the viewing region. The rear face in the viewing region may be, for example, a simple sphere or also a progressive face.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.